Pull in jobspec.cpp and jobspec.hpp. The goal is two-fold.
1. Tightly managing libjobspec from within flux-sched solves odd
make-check errors that we are seeing on some platforms (e.g., Sierra).
The issues seem to arise due to C++ compiler version mismatches.
2. flux-core will transition away from libjobspec anyway
in a near future, and doing this now will help flux-core
make this transition without having to worry about
any breakage in flux-sched.
Name the library as libjobspec_conv.la instead
of libjobspec.la to avoid any name collision
with flux-core's libjobspec.

Integrate yamlcpp check into configure.ac
Drop flux-jobspec check in configure.ac.
Adjust header file inclusion path and makefiles.
Additionally, resource-query and grug2dot utilities commands
are now built in their own folder (instead of from within
their parent folder.

Use intptr_t instead of int64_t to cast the span IDs
that were stored as (void *) in a zlist.
It turned out the int64_t conversion doesn't work for 32-bit
architecture such as armv7l:
$ dpkg-architecture -l | grep HOST_ARCH
DEB_HOST_ARCH=armhf
DEB_HOST_ARCH_ABI=eabihf
DEB_HOST_ARCH_BITS=32
DEB_HOST_ARCH_CPU=arm
DEB_HOST_ARCH_ENDIAN=little
DEB_HOST_ARCH_LIBC=gnu
DEB_HOST_ARCH_OS=linux
On 32-bit systems, it also is unsafe to assign int64_t span_id
directly into void * type.
When you have a very large span id, the value can be truncated
during this assignment.
But in practice, it is very unlikely the id will become larger than
2 billion, the largest value 32-bit integer (through
conversion) can represent. (In particular on 32-bit systems where
the amount of memory would be limited.)
Since we should optimize for 64-bit systems, I still keep
int64_t-to- void* conversion via intptr_t type for now.
If we need to be more serious about supporting 32-bit
architecture, we should take a deeper dive into this topic.

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